Process of treating waste gas-purifying material.



H. GOUTHIERE & P. DUGANGEL. PEoc ss 0F TREATING WASTE (ms PURI FYING MATERIAL.

' APPLICATION FILED JUNE 5", 1911.

1,051,882, 1 Patented Feb14 1913.

F yl- 11 Witnesses; Imgentorg;

HENRI GOUTHIERE AND PIERRE DUCANCEL, OF RHEIMS, FRANCE.

PROCESS OF TREATING WASTE GAS-PURIFYING MATERIAL.

aoaassa Application filed June 5, 1911. Serial No. 631,389.

To all whom it may concern:

Be it known that we, HENRI GOUTHIIERE and PIERRE. DUGANCEL, citizens of the French Republic, residing at Rheims, De-

partment of the Marne, in France, have in-' vented certain new and useful Improvements in Processes of Treating 'VVaste Gas- Purifying Material; and we do hereby de-' clare the following to be a full, clear, and exact description of the invention, such as will enable others'skilled in the art to which it appertains to make and use the same.

The invent-ion relates to a process for permitt-ing the simultaneous extraction of sulfur and cyanids contained in the spent materials which have been used for purifying as. g This process comprises a treatment by an alkaline sulfid or alkaline earth, preferably the neutral ammonium sulfid, so as to form a polysulfid of ammonium. The mass having been filtered, the solution obtained is treatedso as to decompose the polysulfid of ammonium so as to produce sulfur. This decomposition is effected by means of heat, or rather by subjecting the solution to the action of a current of steam which monia very probably forming a double sul- "fid of iron and ammonium. Upon filtermg precipitates the sulfur and entrains the ammonium sulfid which is thus recovered. The residue left in the'filter is immediately diluted with water, then, treated with lime at boiling point excluded from the air. After filtration is left a residue formed of ferric hydroxid and iron sulfid, which, once oxidized in the air, gives a regenerated purifyin material. The exhausted materials whicTz have been used to purify the gas, are added in a cold state to a solution of neu tral ammonium sulfid. The operation is effected in closed receptacles provideij with mechanical agitators. The ammonium sulfid dissolves the sulfur forming a polysulfid of ammonium. It also dissolves the sulfocyanids and renders soluble a quantity of Prussian blue in the form of ammonium ferrocyanidl' lt furthermore transforms the iron oxid into sulfid with fixation of amthe material obtained, a solution is obtained composed of polysulfid of ammonium, of 'ferrocyanids and of sulfocyanids and there remains in the filter a solid residue containing iron sulfid, calcium sulfate, wood saw-dust and the portion of the Prussian Specification of Letters Patent.

yatented Feb. l, 1%13.

blue which was not dissolved by the ammonium sulfid. The solution and the residue are then treated separately. It is preferable to effect the decomposition of the higher sulfid of ammonium by subjecting the solution to the action of aturrent of steam which entrains the ammonium sulfid. The greater part of the latter is thus recovered and can be used for a fresh operation; there remains in the apparatus a residual liquid composed of ferrocyanids, sulfocyanids and containing in suspension precipitated sulfur which is separated by filtration. The solid residue obtained after filtering the purifying material treated by ammonium sulfid is immediately diluted and ammonium, separates and is recovered by the usual means. At the same time the remaining portion of the Prussian blue contained in the residue and not extracted by the ammonium sulfid is. dissolved into calcium ferrocyanid with precipitation of ferric hydroxid. It is of great 1mportance that this residue separated from the solution containing the polysulfid of ammonium should not be exposed to the air and should be immediately diluted with water, because the double sulfid of iron and ammonium which this residue contains would oxidize rapidly in the air giving iron oxid, sulfur and liberating ammonia which would be lost. On the other hand the sulfur formed would give, in the presence of lime and Prussion blue. sulfocyanids which would decrease the yield of ferrocyanid. In order to avoid the action of the air, the preceding operations are undertaken in closed vats provided with mechanical mixers and heating coils. -For the same purpose care should be taken to use as filtering apparatus, pressure filters and mechanical filters with internal collectors, which enables all escape to be avoided. The material obtained after treatment with lime is filtered and gives a solution containing ferrocyanidsl and sulfocyanids of calcium which are extracted by known means, .and a residue containin 'a precipitate of ferric hydroxid, iron sulfid, Wood saw-dust, etc.

The material is allowed to oxidize in the obtained is transformed into vapor in asuitable container, then combined with hydrogen, by admitting the latter to the container,

to form hydrosulfuric acid H S. This acid is absorbed by the ammoniacal solution provided by the treatment with lime and gives neutral ammonium sulfid. In this way the fraction of the latter body, which was decomposed .by,the iron oxid is recovered. This is added to the other portion already obtained due to the decomposition of the solution containing the polysulfid, in order to treat a fresh quantity of the spent material.

The process above described may also, except for certain modifications, be applied to the treatment of spent oxid or criid dammoniaque used for agricultural purposes for destroying insects and weeds. This substance generally contains soluble salts of ammonia,sulfur,sulfoand ferrocyanids and nitrogenous or anic materials. The substance is first treated by ammonium sulfid in accordance with the process described above. By this means there is obtained: 1. A solution of the polysulfid of ammonium containing also sulfur, ammoniacal salts and soluble sulfoand ferrocyanids. 2. A solid residue containing principally v Prussian blue, iron sulfid, calcium sulfate, etc. The solution and the residue are separated by filtration and then treated separately.

. 1. The solution containing the polysulfid of ammonium is decomposed by steam in accordance with the process above described which gives on the one hand regeneratedand on the other hand precipitated sulfur which is separated from the remaining liquid by filtration or decantation, the sulfur being then refined in the usual way. The. residual remaining liquid contains the ammoniacal salts, the soluble sulfocyanids and ferrocyanids, which are decomposed in a still by a wash of barium or calcium sul fid which reacts onv the ammonium sulfate contained in the residual liquid according to the following formula:

and replaces in this way the 10' to 20% fixed during the preceding treatment. The

barium or calcium sulfate is collected in apressure filter, washed, dried and reduced by carbon to the condition of barium or calcium sulfid which is thus regenerated and can be used for the next operation. In this manner the ammonium sulfate formerly contained in the spent oxid or criid dammoniaque is recovered in view of the economical regeneration of the ammonium sulfid. As regards the filtered liquid separated from the barium sulfate, this contains soluble sulfocyanids and ferrocyanids; these are utilized in the manner hereinafter described.

2. The residue resulting from the treatment of the spent oxid or criiddammoniduring the previous treatment and the ferrocyanids and sulfocyanids of ammonium contamed 1n the residual liquid and form a portion of the nitrogenous organic material.

The substance is then filtered and a liquid and residue is obtained. The liquor contains prussiates and sulfocyanids of calcium and the greater part of the dissolved organic nitrogen; this liquor is evaporated to dryness, the product obtained being intimately mixed with its own weight of powdered lime and the whole is subjected to a kind of dry distillation in the presence of a current of steam. Under these conditions all the nitrogen contained. in the residue in the form of prussiate, sulfocyanid or organic nitrogen, is transformed into ammonia which is collected in sulfuric acid in order to form a fresh quantity of ammonium sulfate. This operation is very easy, given the small quantity of foreign matters contained in the extract. Gases rich in ammonia and consequently easily absorbed withoutspecial apparatus are obtained. The saturation of the acid is thus eifected by very hot gases, and evaporation of the solution is produced at the same time which. effects a precipitation of ammonium sulfate. As on the other hand a certain quantity of -hydrosulfuric acid is produced, very probably from the sulfocyanids contained in the extract, the gas is caused to be absorbed by the spent oxid or criid dammoniaque before treat ment by the ammonium sulfid; in this manner the fixation of the latter is diminished. The residue ofthis dry distillation which contains a high quantity of free lime, is

utilized to a great extent in the folloyving" The ammonium sulfid formed is reutilized operation. As regards the. residue se'pa rated from..theiiquid eontaming prussiate 1 of lime, thisis oxidized in air and constitutes a regenerated purifying material which can be used again in gas works. (7)) Instead of treating the residue by a wash of lime it can be mixed with powdered lime and be caused to undergo a kind of dry distillation on the presence of a current of steam. Under these conditions all the nitrogen contained in the residue, either in the shape of Prussian blue or of organic material, is transformed into ammonia which is collected in sulfuric acid to form ammonium sulfate. This distillation is possible by reason of the primary extraction of the sulfur which contains the criid dammoniaque. tion will be different if the criid dammoniaque is heated directly without first removing the sulfur. (0) A third method consists in drying and oxidizing the residue in a closed vessel and collecting in sulfuric acid the ammonia which is set free. The dry residue obtained at the end of this operation contains all the nitrogen of the Prussian blue and of the organic material. It can be advantageously utilized as manure and its agricultural value is increased by reason of the previous elimination of the sulfur and sulfocyanids which are harmful to plant life. Apparatus suitable for carrying out the process is shown in the accompanying drawings, in which Figure 1 shows a diagrammatic view of an apparatus for decomposing ammonium polysulfid by means of steam. Fig. 2 shows a diagrammatic View of the masticating apparatus used.

The apparatus in Fig. 1 comprises a tank 1 which may be heated by' a steam-jacket 2, the steam entering through the pipe 3 and going out through the pipe 4. The solution of polysulfid coming from a suitable receptacle is admitted in the tank by means of a pipe 5 and has an ascendant flow in the tank 1. The liquid leaves this tank by the pipe 6. The steam is admitted by the pipe 7 in a tapered cap 8 covering acup.9, smallnotches 10 being provided for the escapement of the steam; the latter ascends in-the tank 1 and escapes through a pipe 11 drawing along ammonium sulfid resulting from the decomposition of ammonium polysulfid. A drain cook 12 ,is provided at the lower part ofthe tank 1. In practice several apparatus are mounted in series; the pipe '6 of an ap'-" paratus is connected with the pipe 5 of the next one, and the pipe 11 of the first is connected with the pipe 7- of the second. Thus the polysulfid is progressively decomposed an}?i the steam progressively charged 'with su d.

Fig. 2 shows a masticating apparatus 13,

used for treating the spent oxid with ammonium sulfid. This apparatus comprises blades 15 keyed onashaft 14 receiving its motion from a'shaft- 16. The same apparatus is used for" the treatment of the residue by means of lime, but as this reaction is effected at the boiling point a worm 17 is in which passes steam.

\Ve claim used 1. A process for extracting commercial products contained in the spent materials The, condiused for purifying gas comprising the treatused for purifying gas, consisting in t-reating the spent material with an alkaline sulfid,- filtering thesolution, then distilling the filtrate, and filtering-and washing the residue left by'such distillation, thereby obtain ing free sulfur.

3. A process for extracting commercial products contained in the spent materials used for purifying gas, comprising the treating of the spent materials with neutral ammonium sulfid, filtering the solution thus obtained, then distilling the filtrate to form a residue containing sulfur and a distillate containing ammonium sulfid, and then washing and filtering the residue to obtain free sulfur.

4. A process for extracting commercial products contained in the spent materials used 'for purifying gas, comprising the treating of the spent materials with neutral ammonium sulfid, filtering the solution thus obtained, then subjecting the filtrate to a jet of live steam to entrain ammonium sulfid' residue and a distillate, washing the last-.

named residue to obtain free sulfur and then diluting the first-named residue and treating with lime to free ammonia.

6. A process for extracting commercial products contained in the spent materials .used for purifying gas, comprising the treating of the spent materials with neutral ammonium sulfid, filtering the solution thus obtained to form a filtrate and a residue, then distilling .the filtrate to form a second residue and a distillate, washing the lastnamed residue to obtain free sulfur, diluting the first-named residue, treating with lime, filtering to obtain a filtrate composed of ferro-cyanids, and sulfo-cyanids of calcium, the residue being then oxidized to form a compound which can be used again for the purification of the gas.

In' testimony whereof we aifix our slgnatures, in presence of two witnesses.

1 HENRI GOUTHIERE.

PIER RE DUCANCEL. Witnesses:

H. C. Goxn, EMILE KLOTZ. 

